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Vertical distribution of macrozoobenthos within the sediment on the continental slope of the Goban Spur area (NE Atlantic)

Flach, E. and Heip, C.H.R. (1996) Vertical distribution of macrozoobenthos within the sediment on the continental slope of the Goban Spur area (NE Atlantic). Marine Ecology Progress Series, 141, 55-66. ISSN 0171-8630.

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Official URL: http://dx.doi.org/10.3354/meps141055

Abstract

Macrofauna density and biomass were estimated in 4 sediment layers (0-1, 1-5, 5-10 and 10-15 cm) from 12 stations ranging from 185 to 4460 m water depth in the Goban Spur area (NE Atlantic). At the same stations profiles of median grain size, % organic carbon and % total nitrogen were measured to a sediment depth of 15 cm. Macrofauna densities decreased exponentially from similar to 8000 m(-2) at 208 m to similar to 550 m(-2) at the deepest stations (3673 and 4460 m). Most of the macrofauna was concentrated in the upper 1 cm of the sediment. The highest proportion (70 to 80%) was in the upper 1 cm found at intermediate depths (670 to 1425 m), whereas at the deeper stations the fauna was more evenly distributed. Polychaeta were the most abundant taxon, with a high proportion of subsurface deposit-feeders at the deep stations and a high proportion of filter-feeders plus surface deposit-feeders at intermediate depth. Biomass values showed a very variable pattern, mainly due to a few extremely large individuals at some of the stations. Excluding these large individuals, a maximum biomass value was observed around 1000 m water depth. At most stations the biomass was concentrated below the upper 1 cm, which was also reflected in the vertical distribution pattern of the mean individual weight, showing small individuals in the upper 1 cm and larger individuals in the deeper sediment layers. Both density and biomass fell within the range of values usually observed at these depths. Only the biomass value at 1034 m was extremely high and concentrated in the upper 1 cm of the sediment. This may be due to pulsed inputs of fresh material at this station, whereas at the deepest stations (3673 and 4460 m) a constant low input of refractory material supports the fauna of mainly deep-living subsurface deposit-feeders. Median grain size decreased with increasing water depth from similar to 90 pm at 208 m to similar to 8 mu m below 2000 m. The vertical profiles showed very homogeneous sediments to a depth of 15 cm at all stations, probably due to bioturbation by the relatively abundant deposit-feeders. In general, the % of total N and organic C in the upper 1 cm of the sediment increased with increasing water depth, but showed a peak at similar to 1000 m. The % C and especially N were lower in the deeper sediment layers at the deeper stations, resulting in C:N ratios of similar to 12 to 15 in contrast to similar to 7 to 8 in the upper 1 cm of the sediment. The C:N ratio at the midslope stations (similar to 1000 to 1500 m) did not decrease with depth in the sediment, indicating a rapid burial of organic matter by the high numbers of surface deposit-feeders at these stations. [KEYWORDS: vertical distribution; macrozoobenthos; continental slope; grain size; C:N ratio Benthic community; deep; ocean]

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:10397
Deposited On:25 Nov 2011 01:00
Last Modified:14 Oct 2013 11:04

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